The invention relates to compositions for use in patching and filling voids in pavement or concrete and to methods of making and applying the compositions.
Typical compositions which are used to patch and fill voids such as cracks, depressions, potholes, deteriorated joints, and other defects in pavements are composed of an asphaltic binder or adhesive, and a mineral aggregate.
Mineral aggregate is generally defined as various sources of rock, gravel, sand, crushed stone, or cinders that are used in asphalt or concrete compositions to provide the bulk of the composition and to support the loads imposed by traffic. The specific gravity of typical aggregate ranges from approximately 2.5 to 2.8.
The binders used in typical patching mixes are various types of asphalt products. For hot mix patching mixes, asphalt cement is used. For cold applied patching mixes, either emulsified (water based) or cutback (solvent cut) asphalt is used. The function of the binder is to hold the aggregate fraction together to provide a durable product with load carrying capabilities. The specific gravity of typical asphalt binders is approximately 0.99 to 1.04.
Asphalt binders change in stiffness or consistency with variations in temperature. At low temperatures, (typically below 32xc2x0 Fahrenheit (F.)), asphalt binders are stiff and brittle. At high temperatures, (above 100xc2x0 to 150xc2x0 F.) asphalt binders are fluids. The changes in stiffness of asphalt binders are gradual softening with temperature increases, and gradual stiffening with temperature decreases. Typical asphalt binders, when tested for softening point in accordance with ASTM D36, xe2x80x9cTest Method for Softening Point of Bitumen (Ring and Ball Apparatus)xe2x80x9d have values ranging from approximately 100xc2x0 F. for very soft materials to approximately 130xc2x0 F. for very stiff materials. The softening point temperature for asphalt binders indicates the approximate temperature at which it reaches a flowable thick liquid consistency.
Soft asphalts become brittle at lower temperatures then stiffer asphalts.
In patching mixtures, typical proportions of asphaltic binder and aggregate are approximately 5 to 10 percent binder by total weight of the mixture, and 90 to 95 percent aggregate fraction. Due to the differences in specific gravity of the asphalt binder and aggregate, the proportions by volume are different from those indicated by weight. By volume, the proportion of binder typically is 12 to 23 percent and the proportion of aggregate typically is 77 to 88 percent. The specific gravity of typical patching mixes is approximately 2.2 to 2.4, which means the mix typically weighs between approximately 18 and 20 pounds per gallon.
For a typical semi-truck and trailer, maximum shipping loads are limited to approximately 45,000 pounds per truckload. Typical truckloads can generally carry volumes of 4000 to 6000 gallons of lower density materials. However, for typical patching mixtures, this equates to a volume of approximately 2250 to 2500 gallons of mixture that the truck can hold before the 45,000 pound weight limit is reached. This volume range is lower than the truck""s capacity, which means that part of it is empty when hauling typical patching mixtures. Because part of the truck is empty, shipping typical patching mixtures can be costly.
In general, the amount of asphalt binder in the mixture or blend is governed by providing sufficient binder volume for mixture integrity and durability. Too much binder, however, will result in mixture instability during hot weather when the asphalt softens.
Increased amounts of asphalt binder are desirable because it provides increased levels of durability and flexibility to the mixture. However, the maximum amount that can be used usually is limited by the need for adequate high temperature stability.
With amounts of asphalt binder typically used in patching mixtures, there generally is insufficient binder present for the mixture to establish good adhesion to the pavement. Thus, adhesion is generally enhanced by first applying a priming or tacking coat of an asphalt material to the pavement surface.
Typical asphalt and aggregate patching mixtures must be compacted to orient the aggregate particles and increase the density of the patch to provide a stable mixture that resists deformation from applied loads. Compaction is usually accomplished using motorized rollers or tampers designed for that purpose. Typical patching mixtures are also proportioned to contain a certain amount of air voids within the mix after compaction. Typical void amounts range from approximately 5 to 15 percent by volume. The purpose of these voids is to provide additional volume within the mix so that when additional compaction due to traffic loads occurs, the asphalt binder can migrate into the voids. If the voids in a typical patching mix are too low, due to having an excess of asphalt or excessive fines in the aggregate, the material may experience bleeding due to migration of the asphalt binder and instability when subjected to traffic loads. The asphalt binder can tend to migrate under loading at warm summer temperatures due to its softness.
Pavement surface temperatures reached in the summer often reach 140xc2x0 to 160xc2x0 F. At these temperatures, typical asphalt binders can and will flow when subjected to traffic loading, and may bleed.
Small voids that are less than approximately 2 inches wide are typically filled with crack and joint sealers formed of materials such as asphalt binders, polymers and filler. Since the intended use of crack and joint sealers is only to bind and seal cracks and joints, they typically do not contain aggregate. This results in a composition that is too deformable for use in patching and filling intermediate or large voids in pavement, including concrete.
Larger sized pavement voids, greater then approximately 2 inches wide and over 2 inches deep, are typically filled with patching materials, and may require removal of old deteriorated pavement prior to being patched.
There are two known different types of patching mixtures that incorporate differing raw materials and blend compositions. The first is known as Gxc3xcissasphalt. This material is used in Europe as a paving and patching material. Gxc3xcissasphalt is a hot-mixed asphalt composition that uses a specialized aggregate gradation and asphalt cement. The aggregate and gradation uses a high amount of fines (typically approximately 20-25% material finer then a 200 mesh (0.074 mm) sieve), and an amount of asphalt cement binder to produce an essentially voidless mix. To aid in resisting bleeding at warm summer temperatures, relatively stiff asphalt is used. The amount of asphalt used is typically 8 to 11 percent by weight or 19 to 25 percent by volume. The stiff asphalt produces a mix that is not very flexible at low temperatures. The Frass Breaking Point (IP 80/53) for the asphalt binder used in Gxc3xcissasphalt has been reported to be in the range of 16 to 28xc2x0 F. For standard paving grade asphalts, which are typically more flexible at lower temperatures, results are approximately 0 to 15xc2x0 F. It has also been reported that in order to prevent aggregate segregation, that constant agitation of the Gxc3xcissasphalt mixture is required. Problems with aggregate segregation during application have been reported also, because it is sometimes difficult to achieve continuous agitation.
The second different type of patch material is produced by Viper.
The Viper composition contains approximately 25% binder by weight and approximately 75% standard weight aggregate with a specific gravity of about 2.7. The weight of the aggregate makes the Viper product very costly to ship. Additionally, because the aggregate is so heavy, trucks hauling Viper sometimes cannot be completely filled due to shipping weight restrictions. Moreover, because Viper uses standard weight aggregate, it must be agitated well when mixed or the aggregate will settle. If the aggregate settles, the applied Viper mixture can produce inconsistent results.
In view of the problems discussed above, it is an object of the present invention to provide an asphalt or pavement patching composition that is lightweight, self-adhesive, and flexible.
It is another object of the present invention to provide an asphalt or pavement patching composition that is easily applied to voids in need of repair.
It is another object of the present invention to provide an asphalt or pavement patching repair composition that may be applied without priming the surrounding asphalt or concrete.
It is a further object of the present invention to provide an aggregate containing asphalt or concrete repair composition that is lightweight.
It is an advantage that the pavement patching composition of the present invention is lightweight such that it maximizes the volume that can be shipped in a single truckload and reduces shipping costs.
It is another object of the present invention to utilize a binder made of an asphalt modified by the addition of at least one polymer to provide good flexibility, impact resistance, and adhesion.
It is another object of the present invention to utilize a binder that is highly modified by polymer.
In accordance with these objectives, the pavement patch composition of the present invention is an adjustable, hot-applied, self-adhesive, water-resistant composition for the maintenance and repair of voids in concrete or pavement. The pavement patch composition comprises a highly modified polymer asphalt binder and a lightweight aggregate. Variations in the formulation of the polymer asphalt binder allow the pavement patch composition to be specifically tailored for use in cold, moderate, or hot climates. In addition, the type and size of lightweight aggregate may be varied depending upon the desired use of the pavement patch composition. For example, finer aggregate is preferably used for patching small voids, but coarser and larger aggregate is preferred for use in larger voids.
It is an advantage of the pavement patch composition of the present invention in that it can be used to patch voids in asphalt pavement and concrete pavement.
It is another advantage of the pavement patch composition of the invention to provide a patch that includes an aggregate that is lightweight, makes up a significant volume of the patch, and which does not easily settle during application resulting in a patch that is more uniform and homogenous, has good wear resistance, and which possesses good impact toughness.
It is another advantage of the pavement patch composition of this invention that it is simple and economical to make and easy to use.
It is still another advantage of the pavement patch composition of this invention in that its constituents can be tailored for the climate of the region in which it is to be applied.
It is still another advantage of the pavement patch composition of this invention in that its constituents can be tailored for the particular vehicle traffic or loading conditions that will be encountered.
In one preferred embodiment, the pavement patch composition is formed by mixing lightweight aggregate with a hot, highly modified polymer asphalt binder. The hot mixture is then shaped into specifically measured portions and allowed to cool into a solid form. In use, the solid form is heated to a flowable state and applied to or poured into the voids in need of repair. The hot composition is then allowed to cool to form a flexible, weight bearing, water resistant, long lasting pavement patch.
The pavement patch composition is ideally used to repair mid-size voids including, but not limited to, cracks, depressions, raveled areas, and alligator cracks.
The pavement patch composition provides an alternative for repairing voids larger than cracks and joint gaps, which are typically filled with crack and joint sealant, and larger voids such as those repaired with pothole patch methods or by total replacement of the pavement section. The pavement patch composition comprises a lightweight aggregate and a highly modified polymer binder. Unlike conventional pavement patch compositions, the formulation of the asphalt binder of the present invention is variable for use in warm, moderate or cold climates. In its preferred embodiment, the asphalt binder comprises asphalt, polymer, and surfactant. In addition, the binder can contain processing oil. It can also contain other additives.